Warned about danger of gangster carrying gun? (7)
I believe the answer is:
Here is my best explanation:
'warned' is the definition.
(alarming is a kind of warning)
'about danger of gangster carrying gun?' is the subsidiary indication.
'about' says the letters should be written backwards.
'danger of gangster' becomes 'dela' (I can't explain this - if you can you should believe this answer much more).
'carrying' is an insertion indicator.
'gun?' becomes 'arm' (I've seen this in other clues).
'dela' reversed gives 'aled'.
'aled' enclosing 'arm' is 'alarmed'.
(Other definitions for alarmed that I've seen before include "Terrified", "Anxious; disturb", "Given a turn", "Worried", "like Icarus as wax melted?", "In a panic", "Frightened, scared", "Frightened, disturbed", "Fear-stricken" and "Startled".)